BACKGROUND Over 100,000 VHA patients receive oral anticoagulation therapy (OAT) each year. It is known that OAT is safer and more effective when patients spend a more time in the therapeutic range (TTR). However, VHA sites of care vary widely on TTR, from 70% time in range (excellent control) to below 40% (poor control). Our previous efforts to adjust TTR for case mix have had certain limitations, and we need to know more about what sites might do to improve their TTR. OBJECTIVES 1) Improve our risk adjustment model for TTR 2) Study the relationship between site-level processes of care and site-level performance on risk-adjusted TTR (RA-TTR) 3) Develop and pilot a tool to report each site's performance and opportunities for improvement. METHODS We will include all patients who received OAT from the VHA during the study period. We will compute TTR for each patient and mean TTR for each site of care. Aim 1) We will improve our risk adjustment model by adding severity levels to comorbid conditions. We hypothesize that more severe manifestations of comorbid conditions will have a greater impact on TTR. We will also improve our model by using VA-Medicare data to improve the accuracy of patient race, date of warfarin inception, and hospitalizations. It is important to accurately know the date of warfarin inception, because control improves over time for each individual patient. Hospitalizations are known to perturb anticoagulation control; we will disregard anticoagulation testing for 14 days after any VA or non-VA hospitalization. Aim 2) We will study the impact of five process measures on site-level anticoagulation control. Three of these measures relate to the site mean follow-up interval after a low (d1.5), in-range (2-3), or high (e4.0) INR test. One measure relates to the site mean INR value, which reflects whether the site systematically targets an INR of 2.5 (as per clinical guidelines) or tends to shade them lower or higher. The final measure relates to the proportion of patients receiving substantial monitoring of anticoagulation both inside and outside the VHA. We hypothesize that the ideal follow-up times to improve site-level TTR will be less than 28 days after an in-range value and less than 7 days after an extreme value. We hypothesize that sites with a mean INR at or near 2.50 and that sites with little or no co-management with non-VA clinicians will have the best control. Aim 3) We will develop and pilot a report for each site that summarizes the site's current performance on RA-TTR and the expected improvement from various changes in the process measures from Aim 2. We will pilot test these reports with VA clinical leadership to solicit feedback from end users. We hypothesize that each site will have a unique pathway to quality improvement. ANTICIPATED IMPACT Improving the anticoagulation control in the VHA could prevent thousands of adverse events each year, but quality improvement must begin with accurate quality measurement. Our improved risk-adjustment model will ensure that sites treating challenging patients are not penalized. In addition, we will learn important lessons about the impact of comorbid conditions on anticoagulation control, including alcohol abuse, cancer, and mental health conditions. This project will provide the first empirical evidence regarding ideal follow-up intervals in the management of anticoagulation, and will relate these to changes in performance by site. We will detail the impact of care fragmentation between VA and non-VA care upon anticoagulation control, an important safety issue for VA patients. Finally, we will develop and pilot a tool to communicate our recommendations for quality improvement to each site. This tool will eventually serve as the basis for a project to improve anticoagulation care throughout the VHA.